Process for production on nonuniformly intensely colored paper and paper obtainable by such process

ABSTRACT

The present invention relates to a process for the production of nonuniformly intensely colored paper with improved printing or lettering features, and paper produced by this process.

The present invention relates to a process for the production ofnonuniformly intensely colored paper with improved printing or letteringfeatures, and the paper produced by this process.

Even in the age of electronic data transmission, there is in general aneed for visually appealing papers. It is therefore an objective of thepaper industry to produce papers which have an appealing visual effectin addition to high paper quality.

In U.S. Pat. No. 4,534,157, a paper is printed in color in the moiststate directly after its production as a paper web, by applying ink viaink nozzles onto an inking roller which then transfers the ink to thepaper. Thus, an irregular, diffuse pattern with an ink quantity whichremains constant over the paper web is applied to otherwise uncoloredpaper.

In EP 601 517, white paper is printed in regular or irregular patternswith as little ink as possible. The ink penetrates only to a smallextent into the paper. The disclosure of EP 601 157 attaches particularvalue to the small penetration of the ink into the paper, since thepaper is subsequently to be recyclable as white paper. The ink shouldtherefore be capable of being easily removed from the paper.

EP 681 060 describes a process for the production of a differentlycolored paper, in which cellulose fibers and agglomerates of differentthickness are used in the process for the production of the paper andare deposited on or incorporated into the finished paper. The cellulosefibers or agglomerates of different thickness are colored before thedeposition on or incorporation into the paper, and are then introducedinto the paper pulp, which itself may have a different color.

The methods used to date for the production of patterned papers areeither complicated or slow in the production method or lead to paperswhich achieve a completely different effect.

EP 439 363 discloses a paper which contains a desizing agent or iscoated therewith, with the result that better absorption of the inkduring the printing of the paper by means of inkjet printing isachieved. The desizing agent is distributed in/on this paper, uniformlyover the entire paper surface, in order to obtain an optimum printedcopy.

EP 518 490 describes ink which is used for inkjet printing, the inkcontaining a composition which facilitates the penetration of the inkinto the printed paper.

Common to the teachings of EP 439 363 and EP 518 490 is that thepenetration of polar liquids, such as inkjet inks, into the paperstructure and into the paper fibers of sized paper is facilitated by thesuitable use of a desizing agent. However, neither EP 439 363 nor EP 518490 describes the production of patterned paper by nonuniform coloringof the paper surface.

For increasing the printing and lettering features of base paper EP 1239 077 proposes to apply a nonionic surfactant with a polyalkoxylenestructure.

EP 732 219 discloses a printing medium comprising a liquid-absorbentbase material, an ink-receiving layer provided on the base material,which comprises a pigment, a binder and a cationic substance, and asurface layer provided on the ink-receiving layer composed of cationicultrafine particles as inorganic particles. As the ultrafine particlesoxides of metals with a diameter ranging from 1 to 500 nm are described.These particles form a closed glossy surface layer. The pigmentscontained in the ink-receiving layer are inorganic pigments with adiameter ranging from 0.1 to 20 μm.

It was an object of the present invention to obtain a visually appealingpaper of nonuniform coloring with improved printing or letteringfeatures with as little production effort as possible.

This object is achieved by a process for the production of nonuniformlyintensely colored paper, comprising

-   -   a) application of at least one surfactant or a mixture of        surfactants in the form of a latent image or pattern to paper,        whereby the surfactant(s) is/are mixed with at least one filler        (pigment),    -   b) coloring of the paper by means of a dye solution and    -   c) drying of the colored paper.

The invention makes use of the phenomenon of paper sizing and thepossibility of subsequently manipulating this in a specific manner inpreferred regions on the paper web by applying suitable substances.Papers are as a rule sized for the purpose of avoiding excessivepenetration of applied liquids into the paper structure and into thefibers (blotter effect). This is effected during the paper production byadding sizing substances to the aqueous paper fiber slurry before thisis shaped into a paper web in the paper machine. The sizing substancesare deposited on the fibers to the extent to which the property ofliquid absorption of the finished dry paper is desired. This process isknown as internal sizing or engine sizing. The achieved extent of liquidabsorption is inversely proportional to the “degree of internal sizing”of the paper.

Surface sizing can be carried out instead of or in addition to enginesizing. Here, film-forming substances, such as solutions or dispersionsof converted starches, gums and modified polymers, are applied to thealready shaped paper web, for example by means of size presses insidethe paper machine. The surface sizing also contributes to the strengthof the paper, so that high-quality printing paper frequently has enginesize and surface size. The presence of a surface size is, however, notessential for the process according to the invention, and it is alsopossible to use paper which has no surface size.

Alternatively, the process for the production of nonuniformly intenselycolored paper in step a) may comprise the application of a dye solutionin the form of a visible image or pattern to paper.

Preferred embodiments of the invention are stated in the subclaims.

The production process according to the invention leads to a paper whichis solidly colored, the intensity of the color differing within thepaper surface. The different intensity of the color results in a visualeffect which appears as an image or pattern to the eye.

The image or pattern may be present in the form of a representativeimage, an imaginative structure, a signet, a regular or irregularpattern, a net structure or an irregular, for example random,distribution of the color on the paper.

The image or pattern can be applied either directly after papermaking,i.e. to the still moist paper, or to a previously produced, dried paper,the paper then being solidly colored by means of an aqueous dyesolution. The image or pattern can be applied to a continuous paper webor to individual paper sheets. Preferably, the image or pattern isapplied to a continuous paper web.

The image or pattern can be applied by any desired method, in particularby inkjet printing, offset printing, flexographic printing, gravureprinting, printing with felt or rubber rollers, by spraying on ormanually, the last method being unsuitable for industrial production.Particularly preferred application methods for the image or pattern isapplication by means of inkjet printing, flexographic printing orgravure printing.

The pattern or image is applied either in the form of a latent image orpattern or in the form of a visible image or pattern to the paper.

For the creation of a latent image or pattern, a substance whichinfluences the penetration of an aqueous dye solution into the paper atthe point at which the substance is applied by either facilitating orreducing the absorption, is applied to the paper.

This is achieved by reducing (desizing agent) or increasing (waterrepellent), by means of the applied substance, the degree of sizing ordegree of water repellency achieved by the paper sizing.

Every substance which has this property can be used for the processaccording to the invention. Surfactants are preferably used for thispurpose. Anionic, cationic, nonionic or amphoteric surfactants may beused. In addition to the surfactants, it is possible to use substanceswhich facilitate the penetration of dyes into the paper. Such substancesare, for example, glycol ethers, such as ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monophenylether, diethylene glycol monomethyl ether, diethylene glycol monoethylether and diethylene glycol monobutyl ether.

Suitable desizing surfactants can be selected, for example, from (1)hydrophilic polydialkylsiloxanes, (2) polyalkylene glycol, (3)polypropylene oxide/polyethylene oxide copolymers, (4) fattyester-modified compounds of phosphate, sorbitan, glycerol, polyethyleneglycol, sulfosuccinic acids, sulfonic acid or alkylamine, (5)polyoxyalkylene-modified compounds of sorbitan esters, fatty amines,alkanolamides, castor oil, fatty acid, fatty alcohol, (6) quaternaryalcohol sulfate compounds, (7) fatty imidazolines, (8)polyether-modified trisiloxanes and (9) mixtures thereof.

Specific examples of water- or alcohol-soluble desizing agents from theabovementioned classes of substances are, for example, (1)poly(oxyalkylene) modifications of (a) sorbitan esters (e.g. AlkamulsPSML-4 (poly(oxyethylene)sorbitan monolaurate), Alkamuls PSMO-20(poly(oxyethylene)sorbitan monooleate), Alkamuls PSTO-20(poly(oxyethylene)sorbitan trioleate), Alkaril Chemicals); (b) fattyamines (e.g. Alkaminox T-2, T-6 (tallow amine oxyethylate), AlkaminoxSO-5 (soybean amine oxyethylate), Alkaril Chemicals), (Icomeen T-2,Icomeen T-15, ICI Chemicals); (c) castor oil (e.g. Alkasurf CO-10,Alkasurf CO-25B (castor oil oxyethylates), Alkaril Chemicals); (d)alkanolamide (e.g. Alkamide C-2, C-5 (coconut oil alkanolamideoxyethylates), Alkaril Chemicals); (e) fatty acids (e.g. Alkasurf 075-9,Alkasurf 0-10, Alkasurf 0-14 (oleic acid oxyethylates), Alkasurf L-14(lauric acid oxyethylates), Alkasurf P-7 (palmitic acid oxyethylates),Alkaril Chemicals); (f) fatty acid alcohol (e.g. Alkasurf LAN-1, LAN-3,Alkasurf TDA-6, Alkasurf SA-2 (linear alcohol oxyethylates), AlkasurfNP-1, NP-11, Rexol 130 (nonylphenol oxyethylates), Alkasurf OP-1, OP-12(octylphenol oxyethylates), Alkasurf LA-EP-15, Alkasurf LA-EP-25,Alkasurf LA-EP-65 (linear alcohol oxyalkylates)); (2) hydrophilicpoly(dimethylsiloxanes), such as, for example, (a)poly(dimethylsiloxane) provided with a monocarbinol terminal group(PS556, Petrarch Systems Inc.) and poly(dimethylsiloxane) provided witha dicarbinol terminal group (PS555, PS556, Petrarch Systems Inc.); (b)poly(dimethylsiloxane)-b-poly(methylsiloxane/alkylene oxide) copolymers(PS 073, PS 072, PS 071, Petrarch Systems Inc.), Alkasil HEP 182-280,Alkasil HEP 148-330 (Alkaril Chemicals), nonhydrolyzable copolymerscontaining Si—C bonds; (c) poly(dimethylsiloxane)-b-poly(propyleneoxide)-b-poly(ethylene oxide) copolymers (Alkasil NEP 73-70, AkarilChemicals), a hydrolyzable copolymer containing Si—O—C bonds; (d)polyquaternized poly(dimethylsiloxane) copolymers (which can be obtainedby the addition reaction of an α,ω-hydrogenpolysiloxane with epoxidescontaining olefinic bonds and subsequent reaction of the product with adiamine); (3) fatty imidazolines and their derivatives, such as, forexample, (a) Alkazine-0 (oleyl derivative); (b) Alkazine TO (tall oilderivative); (c) Alkateric 2C1B (dicarboxylic acid coconut imidazolinesodium salt), Alkaril Chemicals; (d) Arzoline-4; (e) Arzoline-215, BakerChemicals; (4) fatty acid esters of (a) phosphates (e.g. AlkaphosB6-56A, Alkaril Chemicals); (b) sorbitan (e.g. Alkamuls STO (sorbitantrioleate), Alkamuls SML (sorbitan monolaurate), Alkamuls SMO (sorbitanmonooleate), Alkaril Chemicals); (c) glycerol compounds (e.g. AlkamulsGMO-45LG (glyceryl monooleate), Alkamuls GDO (glyceryl dioleate),Alkamuls GTO (glycerol trioleate); (d) poly(ethylene glycols) (Alkamuls600 DO (dioleate), Alkamuls 400-ML (monolaurate), Alkamuls 600 MO(monooleate), Alkamuls 600 DL (dilaurate), Alkamuls 600 DT (ditallow),Alkaril Chemicals); (e) sulfosuccinic acid (e.g. Alkasurf SS-O-75(sodium dioctylsulfosuccinate), Alkasurf SS-DA4-HE (oxyethylated alcoholsulfosuccinate), Alkasurf SS-L7DE (sodium sulfosuccinate ester of lauricacid diethanolamide), Alkasurf SS-L-HE (sodium laurylsulfosuccinate),Alkaril Chemicals); (f) sulfonic acid (e.g. Alkasurf CA (calciumdodecylbenzenesulfonate), Alkasurf IPAM (isopropylaminedodecylbenzenesulfonate), Alkaril Chemicals); (g) alkylamines (e.g.Alkamide SDO (soybean diethanolamide), Alkamide CDE(coco-diethanolamide), Alkamide 2104 (coconut fatty aciddiethanolamide), Alkamide CMA (coco-monoethanolamide), Alkamide L9DE(lauryldiethanolamide), Alkamide L7Me (lauryl-monoethanolamide),Alkamide LIPA (laurylmonoisopropylamide), Alkaril Chemicals); (5)quaternary compounds, such as, for example, (a) nonpolymeric quaternizedammonium ethosulfate (e.g. Finquat CT, Cordex T-172, FinetexCorporation); (b) quaternary dialkyldimethyl methosulfate (e.g. AlkaquatDHTS (hydrogenated tallow)); (c) alkoxylated quaternized di-fattymethosulfate (e.g. Alkasurf DAET (tallow derivative)); (d) quaternizedfatty imidazoline methosulfate (e.g. Alkaquat T (tallow derivatives),Alkaril Chemicals); (6) water-soluble copolymers of lipophilicpoly(propylene oxide) with hydrophilic poly(ethylene oxide), such as,for example, (a) methanol-soluble Tetronic 150R1, Pluronic L-101,Tetronic 902, Tetronic 25R2 (BASF Corporation), Alkatronic EGE-1(Alkaril Chemicals); (b) water-soluble Tetronic 908, 50R8, 25R8, 904,90R4, Pluronic F-77, all from BASF Corporation, and Alkatronic EGE 25-2and PGP 33-8 from Alkaril Chemicals; (7) poly(alkylene glycol) and itsderivatives, such as, for example, (a) polypropylene glycol (Alkapol PPG425, Alkapol PPG-4000, Alkaril Chemicals); (b) poly(propylene glycoldimethacrylate), poly(ethylene glycol di acryl ate), poly(ethyleneglycol dimethacrylate), poly(ethylene glycol monomethyl ether),poly(ethylene glycol dimethyl ether), poly(ethylene glycol diglycidylether) (all from Polysciences); (c) poly(1,4-oxybutylene glycol)(Scientific Polymer Products) and the like.

Preferred desizing agents include linear alcohol oxyethylates (e.g.Alkasurf LA-EP-65, LA-EP-25 and LA-EP-15 obtainable from AlkarilChemicals), nonylphenol oxyethylates (e.g. Alkasurf NP-11 obtainablefrom Alkaril Chemicals and Rexol 130 obtainable from Hart Chemicals),octylphenol oxyethylates (e.g. Alkasurf OP-12 obtainable from AlkarilChemicals), oleic acid oxyethylates (e.g. Alkasurf 0-14 obtainable fromAlkaril Chemicals), poly(dimethylsiloxane)-b-poly(propyleneoxide)-b-poly(ethylene oxide) copolymers (e.g. Alkasil NEP 73-70obtainable from Alkaril Chemicals), castor oil oxyethylates (e.g.Alkasurf CO25B obtainable from Alkaril Chemicals),coco-imidazolinedicarboxylic acid sodium salts (e.g. Alkateric 2C1Bobtainable from Alkaril Chemicals) and coconut fatty acid diethanolamide(e.g. Alkamid S104 obtainable from Alkaril Chemicals). The Alkasurfdesizing agents are advantageously biodegradable.

Suitable surfactants imparting water repellency are, for example, papersizes, such as alkylsuccinic anhydride (ASA), alkylketene dimer (AKD)and polyolefins (e.g. SÜDRANOL 200, Süddeutsche Emulsions-Chemie GmbH,Mannheim, Germany), waxes, wax-like substances, metal soaps (stearates),paraffin and paraffin emulsions, fatty acids, fatty acid (methyl)esters, fatty alcohols, fatty alcohol polyglycol ethers and the sulfatesthereof.

During application to the paper, the surfactants are present in the formof solutions, emulsions or dispersions, which further may containsoluble dyes as mentioned below, and/or further auxiliaries in additionto surfactants. Conventional auxiliaries are thickeners, such as, forexample, gum arabic, polyacrylates, polymethacrylates, polyvinylalcohols, hydroxypropylcellulose, hydroxyethylcellulose,polyvinylpyrrolidone, polyvinyl ether, starch, polysaccharides and thelike, optical brighteners, brightener quenchers, pigments (dying ornon-dying pigments, including pigments with a metallic effect ormetals), binders, preservatives and safety chemicals, such as, forexample, fluorescent, phosphorescent or luminescent substances. Thesurfactants are preferably present as an aqueous or alcoholic solution.

The concentration ranges for the surfactants in the solutions, emulsionsor dispersions to be applied are 0.01 to 30% by weight, preferably 0.1to 25% by weight, particularly preferably in the range from 0.2 to 15%by weight.

According to the present invention the applied solution, dispersion oremulsion contains further at least one filler (or pigment), which isselected from oxides of metals or semimetals as for example magnesium,calcium, aluminium, zinc, chromium, iron, copper, tin, lead ormanganese. Preferred pigments are silica, gibbsite, bayerite,nordostrandite, boehmite, pseudoboehmite, diaspore, alumina,particularly corundum, alumina hydrate, magnesium silicate, basicmagnesium carbonate, titanium (di)oxide, zinc oxide, aluminium silicate,calcium carbonate, talc, clay, hydrotalcite, inorganic matters such asdiatomite, organic matters such as resinous pigments made ofurea-formalin resins, ethylene resins, styrene resins, acrylate resinsor combinations thereof.

One aspect of the invention is that the fillers (pigments) used have alarge surface area. The particles themselves, however, have a diameterranging from 1 to 500 nm, preferably from 10 to 100 nm.

The addition of the filler to the solution, emulsion or dispersioneffecting the latent image or pattern has the effect that the printingor lettering on that parts of paper which are treated with thesurfactant is improved. By treating the paper with a surfactant laterapplied ink disperses on that parts which are treated (bleeding,feathering). This effect is reduced by simultaneously applying thesurfactant and a filler, since less surfactant is necessary forobtaining the same image or pattern effect when simultaneously a filleris applied. Due to less amount of surfactant(s) less dispersing of theprinting or lettering ink is observed. The ratio of filler andsurfactant in the applied solution, emulsion or dispersion is 1:0,08 to1:0,9, preferably 1:0,09 to 1:0,5, more preferably 1:0,1 to 1:0,4referred to the solid parts (dry).

The applied fillers (pigments) preferably are non-colored, morepreferably are transparent and they have a diameter which is so smallthat no reflection or light dispersion is obtainable. The preferredaverage diameter of the particles is less than 0.1 μm. Therefore thepigments form a colloidal solution in aqueous systems.

Particularly preferred are cationic fillers, which means that thepigments have positive charge on their surface. Those having negativecharge on their surface like silika may also be used if they aresurface-treated to change the negative charge on the surface to apositive charge. The positive charge on the cationic surface effects aincreased binding of negatively charged dyes of the following dyingbath. In this preferred embodiment nonionic surfactants are used inmixture with the cationic fillers.

The concentrations of the thickeners which can be used as surfactantauxiliaries are in the range from 0 to 5% by weight, preferably 0.01 to2.5% by weight, particularly preferably 0.05 to 2.5% by weight, of thetotal solution, emulsion or dispersion.

In order to achieve a further special effect on the finished paper,desizing and water repellency-imparting surfactants may also be appliedside by side on the same paper surface.

Any desired dye solution can be used for creating a visible image orpattern. An aqueous solution of substantive, basic or acidic dyes, or amixture of these dyes, is preferably used. Examples of suitable dyesolutions are customary printing inks which contain, for example,anthraquinone-, monoazo-, diazo-, phthalocyanine-, aza-(18)-annulene-and formazan-copper complex dyes. Examples of suitable dyes are thosementioned further below for the dye solution of the dyeing bath,including dyes containing or based on pigments as mentioned below.

The concentration ranges of the dyes are 0.1 to 30% by weight,preferably 1.0 to 20% by weight, particularly preferably 2.0 to 10% byweight.

The latent or visible image or pattern can be applied to one side orboth sides of the paper so that the finished paper has, at least on oneside, a color which is more intense or less intense than in theuntreated regions of the paper surface(s).

After the application of the latent or visible image or pattern to thepaper, the paper is solidly colored in step (b) with the aid of a dyesolution. This coloring is effected so as to cover the whole area,either inside or outside the paper machine, by applying dye solution(s)to the paper by means of classical paper coating apparatuses andprocesses, such as, for example, a size press, film press, knife coater,blade, rolls or spraying, or by application of a dye solution to thetotal surface of the paper with the aid of suitable printing methods,such as inkjet printing, offset printing, flexographic printing, gravureprinting or printing by means of felt or rubber rollers, by spraying onor by tub coloring of the paper in a dyeing bath. It is preferable tocolor the paper by the dip process in an aqueous dye solution.

Any dye solution commercially available for these purposes can be usedin the present invention. The dye solution usually contains the dyes inconcentration ranges of 0.1 to 40% by weight, preferably 0.1 to 35% byweight, very particularly preferably 0.1 to 30% by weight. Theconcentration of the dye solution can be established according to theindividually desired effect to be achieved (intensity of thesubsequently desired image).

Corresponding experiments can be carried out by any person skilled inthe art by simple testing.

In the dip process, the paper is immersed in an aqueous dye solutionafter application of the latent or visible image or pattern and is thenpressed off and dried. Tub coloring can be carried out using sized orunsized paper webs or paper sheets. By means of tub coloring, it ispossible to obtain rich colors of very high luminous power. A furtheradvantage of this method is that even small amounts can be coloredwithout operating inefficiently.

If a latent image was applied before the coloring of the paper, thepaper absorbs the color to a greater or lesser extent in the pretreatedareas during the coloring process, depending on the substance with whichthe paper was pretreated.

The stronger acceptance of the ink in regions which were pretreated witha desizing agent gives the paper on which the image or pattern initiallyapplied in latent form appears in a more intense hue of the same colorin which the entire paper is colored. Thus, the color intensity of theimage or pattern subsequently appearing as “positive” can be varied bythe applied amount and/or composition of the desizing agent applied.

If a water repellent is applied before the coloring of the paper, theimage or pattern initially applied in latent form appears, after thecoloring of the paper, in a less intense hue of the same color in whichthe entire paper is colored. Here too, the color intensity of the imageor pattern subsequently appearing as “negative” can be varied by theapplied amount and/or composition of the water repellent applied.

For the production of the latent image, it is also possible to applydesizing and water-repellent substances side by side on the same papersurface, so that the finished paper has both “positive” and “negative”images or patterns.

In order to obtain one of the effects described so far, it is essentialto carry out the coloring of the paper after the application of thesubstance influencing the ink absorption.

If a visible image or pattern is applied before the coloring of thepaper, the subsequent coloring of the paper intensifies the color of thepreviously applied image or pattern, so that a special effect, namelythe nonuniformly intense coloring of the paper, can also be achievedthereby. This effect can be obtained only if the paper carrying thevisible image is additionally colored.

Customary aqueous dye solutions can be used for coloring the paper.These may contain basic and/or acidic and/or substantive dyes. Examplesof suitable dye solutions are solutions which contain anthraquinone-,monoazo-, diazo-, phthalocyanine-, aza-(18)-annulene- andformazan-copper complex dyes. Specific examples of suitable dyes arementioned in EP-A 559 324, on page 4, lines 25 to 53. These are inparticular triphenodioxazines, Bernacid Red 2BMN; Pontamine BrilliantBond Blue A; Pontamine; Food Black 2; Carodirect Turquoise FBL SupraConc. (Direct Blue 199), obtainable from Carolina Color and Chemical;Special Fast Turquoise 8GL Liquid (Direct Blue 86), obtainable fromMobay Chemical; Intrabond Liquid Turquoise GLL (Direct Blue 86),obtainable from Crompton and Knowles; Cibracron Brilliant Red 38-A(Reactive Red 4), obtainable from Aldrich Chemical; Drimarene BrilliantRed X-2B (Reactive Red 56), obtainable from Pylam, Inc.; LevafixBrilliant Red E-4B, obtainable from Mobay Chemical; Levafix BrilliantRed E-6BA, obtainable from Mobay Chemical; Procion Red H8B (Reactive Red31), obtainable from ICI America; Pylam Certified D&C Red #28 (Acid Red92), obtainable from Pylam; Direct Brill Pink B Ground Crude, obtainablefrom Crompton & Knowles; Cartasol Gelb GTF, obtainable from Sandoz,Inc.; Tartrazine Extra Conc. (FD&C Gelb #5, Acid Yellow 23), obtainablefrom Sandoz; Carodirect Yellow RL (Direct Yellow 86), obtainable fromCarolina Color and Chemical; Cartasol Yellow GTF Liquid Special 110,obtainable from Sandoz, Inc.; D&C Yellow #10 (Acid Yellow 3), obtainablefrom Tricon; Yellow Shade 16948, obtainable from Tricon, Basacid BlackX34, obtainable from BASF, Carta Black 2GT, obtainable from Sandoz,Inc.; Direct Brilliant Pink B (Crompton-Knolls); Kayanol Red 3BL (NipponKayaku Company); Levanol Brilliant Red 3BW (Mobay Chemical Company);Levaderm Lemon Yellow (Mobay Chemical Company); Spirit Fast Yellow 3G;Sirius Supra Yellow GD 167; Cartasol Brilliant Yellow 4GF (Sandoz);Pergasol Yellow CGP (Ciba-Geigy); Dermacarbon 2GT (Sandoz); PyrazolBlack BG (ICI); Morfast Black Conc A (Morton-Thiokol); Diazol Black RNQuad (ICI); Luxol Blue MBSN (Morton-Thiokol); Sevron Blue 5GMF (ICI);Basacid Blue 750 (BASF); Bernacid Red, obtainable from Berncolors,Poughkeepsie, N.Y.; Pontamine Brilliant Bond Blue; Berncolor A.Y. 34;Telon Fast Yellow 4GL-175; BASF Basacid Black SE 0228; the Pro-Jetseries obtainable from ICI, including Pro-Jet Gelb I (Direct Yellow 86),Pro-Jet Magenta I (Acid Red 249), Pro-Jet Cyan I (Direct Blue 199),Pro-Jet Schwarz I (Direct Black 168), Pro-Jet Yellow 1-G (Direct Yellow132), Aminyl Brilliant Red F-B, obtainable from Sumitomo Chemical Co.(Japan), the Duasyn line of “salt-free” dyes obtainable from Hoechst,such as Duasyn Direct Schwarz HEF-SF (Direct Black 168), Duasyn SchwarzRL-SF (Reactive Black 31), Duasyn Direct Gelb 6G-SF VP216 (Direct Yellow157), Duasyn Brilliant Gelb GL-SF VP220 (Reactive Yellow 37), DuasynAcid Yellow XX-SF VP413 (Acid Yellow 23), Duasyn Brilliant Rot F3B-SFVP218 (Reactive Red 180), Duasyn Rhodamine B-SF VP353 (Acid Red 52),Duasyn Direct Turkisblau FRL-SF VP368 (Direct Blue 199), Duasyn AcidBlue AE-SF VP344 (Acid Blue 9), and the like, and mixtures of thesedyes.

Further dyes can be used which contain or are based on pigments (dyingor non-dying pigment), including pigments with metallic effect, ormetals.

The concentration of the dye depends on the manufacturer and also on thecolor used and is not limiting for the present invention.

The dye solutions can moreover contain further additives, such asalcohol, thickeners, wet-strength agents, optical brighteners,preservatives, safety chemicals, binders and pigments (dyes or non-dyingpigments, like for example calcium carbonate). Auxiliaries for the dyesolution are in particular gum arabic, polyacrylate salts,polymethacrylate salts, polyvinyl alcohols, hydroxypropylcellulose,hydroxyethylcellulose, polyvinylpyrrolidone, polyvinyl ether, starch,polysaccharides and the like. Further customary additives for inks maylikewise be present. Such customary additives are mentioned in EP-A 518490, page 4, line 55, to page 5, line 9.

The process according to the invention is to be explained in more detailbelow by the following examples, without it being intended to limit theinvention to the embodiments described here.

EXAMPLES

A paper having a basis weight of 105 g/m² is produced on a Fourdriniermachine. The paper stock composition consists of 80% by weight ofsoftwood sulfate pulp and 20% by weight of eucalyptus sulfate pulp. Thepaper sizing is carried out using rosin size and alum. 1% ofmelamine/formaldehyde resin is used as the wet-strength agent. The paperused in the example has no surface size.

The stated percentages of the nonfibrous additives are based on thefiber content. Sheets are taken from the paper thus produced, anddesizing (example 1) or water-repellent (example 2) or both (example 3)substances are applied in the form of handwritten characters to saidsheets manually with the aid of an application apparatus, for example aFineliner (Rotring Rapidograph 0.35 mm diameter), reed pen or brush. Inexample 4, a visible image is applied to the paper. The sheets treatedin this manner are colored by dipping in a dye solution, then pressedoff with an absorptive paper mat and dried.

Example 1 to 8

Application of a latent image using a desizing agent and a filler:

An aqueous solution of surfactant(s) is applied as described above to apaper sheet. The subsequent coloring is effected by dipping the papersheet into a 1.0% strength by weight aqueous Cartasol Blau 3RF solution(Sandoz Chemikalien AG, Basle/Clariant (Deutschland) GmbH, Lörrach). Thelatent characters are very clearly visible and appear positive and in anintense hue in the same color in which the entire paper is colored.

After drying the paper something is written or printed on the paper andthe result is visibly determined.

The used compounds are:

-   TEGOPREN 5847: A polyether-modified trisiloxane (nonionic surfactant    from GOLDSCHMIDT),-   HYDROPALAT 120 EXP: An EO/PO-modified fatty alcohol, modified fatty    alcohol polyglycolether (nonionic surfactant from COGNIS/Henkel),-   TYLOSE H 30000 YP2: Hydroxyethylcellulose (nonionic thickener from    CLARIANT)-   TYLOSE H 60000 YP2: Hydroxyethylcellulose (nonionic thickener from    CLARIANT)-   WALOCEL CRT 30000: Sodium-Carboxymethylcellulose (anionic thickener    from Wolff Walsrode, BAYER)-   LUDOX CL: Colloidal silica with positive particle charge as    filler/pigment (from Grace Davison).

TABLE 1 The amounts are given in parts per weight Example 0 1 2 3 4 5 67 8 composition Tegopren W 5847 3.0 3.0 1.0 0.5 — — — — — Walocel CRT30000 0.2 — — — — — — — — Hydropalat 120 EXP — — — — 2.0 1.0 0.5 0.5Tylose H 30000 YP2 — 0.2 0.2 0.2 — — — — — Tylose H 60000 YP2 — — — 0.20.2 0.2 0.2 0.2 Ludox CL — — 10.0 10.0 10.0 10.0 10.0 — 10.0 Water 96.896.8 88.8 89.3 87.8 88.8 89.3 99.7 89.8 Bleeding (HP990Cxi) IJ/BlackStrong Strong no no no no no no no Ink (fountain pen) Strong Strong nono no no no no no Dying bath Dying intensity Strong Strong Strong EvenStrong Strong Even weak Extremely Strong Strong weak

1. A process for the production of nonuniformly intensely colored paper,comprising: a) applying by a printing method at least one surfactant ora mixture of surfactants in the form of a latent image or pattern topaper on a continuous paper web, whereby the surfactant(s) is/are mixedwith at least one filler (pigment), selected from oxides of metals orsemimetals, or inorganic matters, or organic matters, or combinationsthereof; wherein the at least one surfactant or a mixture of surfactantsare present in the form of any of solutions, emulsions, and dispersionsin a concentration ranging between approximately 0.01 to 30 wt. % on thebasis of the total weight of the solutions, emulsions, and dispersions;and wherein a ratio of filler to surfactant in the solutions, emulsions,and dispersions ranges approximately from 1:0.08 to 1:0.9; b) coloringof the paper by means of a dye solution; wherein the dye is present in aconcentration ranging between approximately 0.1 to 30 wt. % on the basisof the total weight of the solution; and c) drying of the colored paper.2. The process as claimed in claim 1, wherein the latent image orpattern is produced by applying the surfactant and the filler (mixture)by means of inkjet printing, offset printing, flexographic printing,gravure printing or printing by means of felt or rubber rollers, byspraying on or manually.
 3. The process according to claim 1 wherein thefiller is selected from silica, gibbsite, bayerite, nordostrandite,boehmite, pseudoboebmite, diaspore, alumina, particularly corundum,alumina hydrate, magnesium silicate, basic magnesium carbonate, titanium(di)oxide, zinc oxide, aluminium silicate, calcium carbonate, talc,clay, hydrotalcite, inorganic matters, and organic matters.
 4. Theprocess as claimed in claim 3, wherein the inorganic matters includediatomite.
 5. The process as claimed in claim 3, wherein the organicmatters include resinous pigments made of urea-formalin resins, ethyleneresins, styrene resins, acrylate resins or combinations thereof.
 6. Theprocess as claimed in claim 1, wherein the applied surfactantfacilitates the penetration of water-soluble dyes into the paper.
 7. Theprocess as claimed in claim 1, wherein the applied surfactant reducesthe penetration of water-soluble dyes into the paper.
 8. The process asclaimed in claim 1, wherein, in step a), both a surfactant whichfacilitates the penetration of water-soluble dyes into the paper and asurfactant which reduces the penetration of water-soluble dyes into thepaper are applied.
 9. The process as claimed claim 1, wherein an aqueousdye solution is used in step b).
 10. The process as claimed in claim 9,wherein the coloring in step b) is carried out inside or outside a papermachine by applying dye solution(s) to the paper by means of papercoating apparatuses and methods.
 11. The process as claimed in claim 10,wherein the paper coating apparatuses methods include at least one ofsize press, film press, knife coater, blade, rolls or spraying.
 12. Theprocess as claimed in claim 9, wherein the coloring in step b) iscarried out inside or outside a paper machine by application of a dyesolution to the total surface of the paper with the aid of suitableprinting methods.
 13. The process as claimed in claim 12, wherein thesuitable printing methods include at least one of inkjet printing,offset printing, flexographic printing, gravure printing or printing bymeans of felt or rubber rollers.
 14. The process as claimed in claim 9,wherein the coloring in step b) is carried out inside or outside a papermachine by spraying on or by tub coloring of the paper in a dyeing bath.15. The process as claimed in claim 1, wherein the image or pattern is adiagram, a signet, a regular or irregular pattern, a net structure orany nonuniform color distribution.
 16. The process as claimed in claim1, wherein the metals or semimetals include at least one of magnesium,calcium, aluminium, zinc, chromium, iron, copper, tin, lead andmanganese.